Understanding the drivers of droughts is essential to improve the prediction of these extreme events and develop potential early warning systems and mitigation strategies. Until now, many studies have examined general relationships between precipitation, soil moisture, and large-scale circulation patterns and the causes of individual drought events in Europe. However, there is still much to be understood, particularly about the climatology of the onset and termination (O&T) of droughts in this region. Therefore, here, we investigate the temporal characteristics and atmospheric drivers associated with O&T of soil moisture droughts in southern (SEU) and central Europe (CEU) on the seasonal scale during the period of 1981–2020. We also examine atmospheric mechanisms that intensify droughts from their onsets. 

Different drought indices (SPEI, surface, and root-zone soil moisture anomalies —SM) obtained from various data sources that are based on observations and land surface models (ERA5, ECAD, GLEAM-v3, and GLDAS-2) were used to calculate the duration and seasons of occurrence of O&T. The traditional clustering method, combined with the L-moment correlation analysis, were performed to detect atmospheric drivers in geopotential heights (GP) from ERA5. 

Our results show that the duration of O&T depends on the drought index: it is shorter in SPEI and surface SM but longer in deeper SM, which implies that atmospheric signals do not fully propagate to the deep soil layers. The season of occurrence of O&T depends not only on the drought index but also on the dataset and the region. The difference between the datasets is more pronounced in CEU, showing no common season of occurrence of O&T. In contrast, more O&Ts are likely to occur during the fall and winter in SEU, indicating the importance of precipitation variability during these wet seasons in initiating and terminating droughts. In terms of atmospheric drivers, frequent anticyclonic circulation patterns in central Europe linked with the northward shift and weakening of westerlies are more commonly detected during the onsets. Conversely, the opposite cyclonic circulation condition prevails during the termination periods. Strong increases in regional GP related to the initial development of dry conditions are observed during the onsets. However, during the intensification period, regional GP exhibits little variability with no statistically significant change in the mean values. Surface temperature (T) also changes little during O&T and the intensification period, which may indicate that, on a multi-seasonal time scale, the influence of temperature on droughts is less pronounced than those of the large-scale atmospheric drivers. However, the effect of T becomes significant in the summer. Anomalously high T intensifies the impacts of droughts during the warm seasons in ongoing multi-season droughts. A clear example of this is the multi-season 2015–2020 drought in CEU.

How to cite: Kim, W. M., González-Rojí, S. J., and Simpson, I.: Temporal Characteristics and Atmospheric Drivers of Onset and Termination of Soil Moisture Droughts in Europe, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-65, https://doi.org/10.5194/ems2023-65, 2023.

Changing climatic conditions affect several sectors and processes in the environment, including river discharge. It is important to estimate the probable changes, as it may play an important role in flood defence, ecosystems, transportation, energy supply or water-management. Our ultimate aim is to analyse the runoff conditions in a small European catchment, namely, the Upper-Tisza basin. As a first step of our investigation, climatic conditions are analysed for the target area.

For the analysis the observation-based CARPATCLIM dataset and 11 regional climate model simulations from the EURO-CORDEX program are used. Three 30-year-long time periods are selected (1972–2001, 2021–2050, 2069–2098) and three different scenarios (RCP2.6, RCP4.5, RCP8.5) are applied to analyse the future conditions from an immediate reduction of anthropogenic greenhouse gas emission to a later reduction, and finally no mitigation throughout the 21^st century. Therefore, uncertainties emerging from both the applied model and the applied scenario can be assessed. Temperature and precipitation characteristics are calculated on a monthly basis for the entire domain, and for six hydrological stations (namely, Alsókalocsa, Bisztra, Királymező, Ökörmező, Rahó, Tiszabecs). Beside the mean values, different percentile values and climate indices are determined, e.g. the consecutive dry days, the number of precipitation days with more than 5, 10 and 20 mm, the highest one-day and five-day precipitation amount, the number of cold days and frost days.

According to our results, higher temperature values will occur in the entire area. The greatest warming in the Upper-Tisza basin is projected for January, when temperature increase can exceed 4.6 °C by the end of the 21^st century according to the multi-model mean under the RCP8.5 scenario. Precipitation is projected to increase in winter, while a precipitation decrease in summer is likely to occur according to the RCP8.5 scenario. Higher temperature (which may result in less snow) and altered temporal distribution of precipitation clearly have an effect on runoff conditions, so in order to analyse them in details, the next step of our research is to run the DIWA hydrological model driven by the different climate model simulations.

How to cite: Kis, A., Pongrácz, R., and Szabó, J. A.: Analysing hydroclimatic changes in the Upper-Tisza catchment under mitigation and non-mitigation scenarios, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-208, https://doi.org/10.5194/ems2023-208, 2023.

In this paper future changes of surface water availability in Austria are investigated. We use an ensemble of downscaled and bias-corrected regional climate model simulations of the EURO-CORDEX initiative under moderate mitigation (RCP4.5) and Paris agreement (RCP2.6) emission scenarios. The climatic water balance and its components (rainfall, snow melt, glacier melt and atmospheric evaporative demand) are used as indicators for surface water availability and we focus on different altitudinal classes (lowland, mountainous and high alpine) to depict a variety of processes in complex terrain. Apart from analysing the mean changes of these components we also pursue a hazard risk approach by estimating future changes in return periods of meteorological drought events of a given magnitude as observed in the reference period. The results show in general wetter conditions over the course of the 21^st century over Austria on an annual basis compared to the reference period 1981-2010 (e.g. RCP4.5 +107 mm, RCP2.6 +63 mm for the period 2071-2100). Considering seasonal differences, winter and spring are getting wetter due to an increase in precipitation and a higher fraction of rainfall as a consequence of rising temperatures. In summer only little changes in the mean of the climatic water balance conditions are visible across the model ensemble (e.g. RCP4.5 ±0mm, RCP2.6 -2 mm for the period 2071-2100). On the contrary, by analysing changes in return periods of drought events, an increasing risk of moderate and extreme drought events during summer is apparent, a signal emerging within the climate system along increasing warming.

How to cite: Haslinger, K., Schöner, W., Abermann, J., Laaha, G., Andre, K., Olefs, M., and Koch, R.: Apparent contradiction in the projected climatic water balance for Austria: wetter condition on average versus higher probability of meteorological droughts, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-426, https://doi.org/10.5194/ems2023-426, 2023.

In our digital age, connecting models and data from various components of the earth system becomes more and more important. To this end, it is important to define standards and interfaces facilitate such integration. Here, we present the approach we took for eWaterCycle [1].

eWaterCycle is a fully Open Source system designed explicitly to advance the state of Open and FAIR hydrological modelling. It gives users access to a centralized platform where they can perform hydrological experiments. Complete with data, a suite of models, an interactive scripting environment, and a graphical explorer to quickly setup an experiment.

Hydrological models vary in programming language, their setup and configuration. They require differently defined inputs, and do not have a standard form of output. This makes it challenging to compare and exchange models and their inputs and output. eWaterCycle aims to solve this, so scientists can build upon each other’s work and focus on scientific questions instead of technical details.

Inside eWaterCycle, models are wrapped in a Basic Model Interface and live in their own isolated containers. We developed grpc4bmi  to enable communication with models inside their containers. This means that you can talk to different models, written in a range of programming languages, in a standardized way. ESMValTool is used to generate the meteorological forcing data with reproducible recipes. Discharge observations from the USGS and GRDC are available to validate the models.

The platform comes with comprehensive documentation, including a suite of example notebooks. It also includes setup instructions for system administrators and guidance for incorporating new models. The interface between meteorology and hydrology is most prominent in the forcing generation module. Beyond that, the standards and technology used for the hydrological models in eWaterCycle can be extended to other components of the land-atmosphere continuum.

[1] https://doi.org/10.5194/gmd-15-5371-2022

How to cite: Kalverla, P. C., Verhoeven, S., Schilperoort, B., Alidoost, S., Liu, Y., Drost, N., Aerts, J., and Hut, R.: eWaterCycle as a modelling interface between meteorology and hydrology, EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-480, https://doi.org/10.5194/ems2023-480, 2023.

How to cite: Pillosu, F., Prudhomme, C., and Cloke, H.: Is it possible to identify flash flood risk areas with global model rainfall forecasts? A comparative study for the ECMWF ensemble - raw model versus a point-scale post-processed version., EMS Annual Meeting 2023, Bratislava, Slovakia, 4–8 Sep 2023, EMS2023-611, https://doi.org/10.5194/ems2023-611, 2023.